Almost all of these products all have buttons or cap-touch buttons (or sliders) that control volume up and down. In almost all cases, the volume control is a digital multiplier.

You've obviously never reverse engineered any of these devices if you think this.

Edit: I mean think about what you're claiming. Any modern device can set the line out and headphone out volume independently. Do you really think theres two stereo DACs included just so that they can use independent digital volume adjustments? No, that'd be nuts, the cost would be huge. They have independent volume control because the headphone amp and line out amp volume is software controlled.

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That the usual listening volume of most electronics is at 1/3rd or 1/4th of the max volume is not a reason to say that digital volume wouldn't have enough SNR.

I guess we all are used to hear the background noise of amplifiers when moving the analog volume up. Yet, that denotes te SNR of that device.

The ideal situation is always an analog volume at the end of the chain, but that only lowers the background noise. If the amp is able to have a low enough noisefloor, it wouldn't be necessary. Of course, that makes it costlier.

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I think SNR is probably not the best way to think about consumer electronics anyway. Most of these devices have excellent, nearly quantization noise limited DACs that are far more accurate then is actually useful. Particularly so for anything portable (and thus battery powered).

However, while they'll all give you nearly 16 bit limited performance into a line out, they tend to have fairly limited amplifiers (ignoring Apple, Sandisk which are very good). They also have essentially fixed noise floors that are independent of volume. So a more useful approach is to think about them in terms of the impedance and sensitivity that will give good performance. The noise floor puts a limit on sensitivity, since very high sensitivity headphones will produce more acoustic noise, while the finite output impedance limits how low of an impedance can be driven without distortion.

That said, quality has been increasing. Apple and some other companies will now sell you devices with integrated amps that are better then what passed for entry level dedicated headphone amplifiers 5 years ago.

Almost all of these products all have buttons or cap-touch buttons (or sliders) that control volume up and down. In almost all cases, the volume control is a digital multiplier.

You've obviously never reverse engineered any of these devices if you think this.

Edit: I mean think about what you're claiming. Any modern device can set the line out and headphone out volume independently. Do you really think theres two stereo DACs included just so that they can use independent digital volume adjustments? No, that'd be nuts, the cost would be huge. They have independent volume control because the headphone amp and line out amp volume is software controlled.

Wrong, but your conclusion that two DACs would be required is correct!

The Apple devices use Cirrus CLI158881 Stereo Codecs which are similar to the CS42L73. These devices have two stereo DACs, one stereo ADC, and a digital mixing engine. Such chips form the audio core of almost all portable devices. Digital gain control is ubiquitous.

DAC linearity is important because most portable devices have digital volume controls that reduce the signal before the DAC

And I'm new here and have never taken a DAP apart, but requiring that someone you disagree with undertake the entire burden of proof while you should be assumed correct by default seems a bit much. If you have dissected DAPs with analog volume controls, you should have said which ones and built a case from there.

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All portable electronics have analog volume control, Apple's included. You couldn't buy an mp3 player that had digital volume control if you wanted to. They aren't made.

Absolutely incorrect!

Almost all of these products all have buttons or cap-touch buttons (or sliders) that control volume up and down. In almost all cases, the volume control is a digital multiplier. Very few consumer products still have analog volume controls (variable resistors) in the audio path. DSP is cheap and is already required to do MP3 decoding.

Agreed.

What I find interesting is the fact that 100% of all of the contemporary AVRs that I have examined have both DSPs and digitally controlled analog volume controls.

I have several doubts on what you say an definitely, that formula doesn't help.

The part that confuses me especially is why do you imply that lowering the volume digitally, increases the noise level.

Decreasing the volume with the digital volume control is necessary to reduce the volume to a normal listening level. This decreases the signal, but does not decrease the noise level. Most systems are designed to provide "normal" listening levels at something less than full volume (often 20 dB less than full volume). If you use 20 dB of digital gain reduction, the SNR degrades by exactly 20 dB.

If you do the math, the noise floor of consumer D/A converters is often higher than the ambient noise level in a quiet room when audio is playing at "normal" levels.[/quote]

That would be related to mathematical models whose relevance can and has been disputed for several decades, starting no later than Fielder's ca. 1995 AES paper.

Trouble is that in the real world, being disturbed by noise from the DACs is exceedingly rare. We've got ower 10 years experience with consumers playing video DVDs with 16 bit sound at high listening levels and no widespread complaints about background noise. We have fewer but still a significant number of years of experience with portable digital players with similar results.

When presented with 3 independent well-publicized opportunities to obtain recordings on media with > 16 bits all of the products failed in the mainstream marketplace. It was subsequently found that a very high proportion of those recordings were upsampled recordings that started out with 16 or fewer bits of dynamic range. There were no listener complaints based on just listening until the results of unfavorable technical tests were publicized.

I understand the need for high quality low volume product offerings with far greater capabilities than the minimum that is required for the mainstream market. If nothing else they facilitate the creation of media with the required quality levels since a product can't be better than the means used to create it. These products need not be justified based on the needs of the mainstream market but can make sense even when they vastly exceed the minimum need.

All portable electronics have analog volume control, Apple's included. You couldn't buy an mp3 player that had digital volume control if you wanted to. They aren't made.

Absolutely incorrect!

Name one such product. Just one.

The Apple devices use Cirrus CLI158881 Stereo Codecs which are similar to the CS42L73. These devices have two stereo DACs, one stereo ADC, and a digital mixing engine. Such chips form the audio core of almost all portable devices. Digital gain control is ubiquitous.

Agreed. The usual chips we find in mainstream portable digital audio player and smart phones and tablets generally has at last 4 DACs and 2 ADCs. Even though they are not all used by the specific products, this is also true of the SOC that is the heart of the economically-priced Sansa Clip+ and Fuze.

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Wrong, but your conclusion that two DACs would be required is correct!

The Apple devices use Cirrus CLI158881 Stereo Codecs which are similar to the CS42L73. These devices have two stereo DACs, one stereo ADC, and a digital mixing engine. Such chips form the audio core of almost all portable devices. Digital gain control is ubiquitous.

And I'm new here and have never taken a DAP apart, but requiring that someone you disagree with undertake the entire burden of proof while you should be assumed correct by default seems a bit much.

How exactly do I prove that something doesn't exist? I can point out that I've worked on drivers for lots of these devices and not one of them uses digital gain control, but I can't really prove it since I haven't worked on every single device in existence, just a lot of them.

Agreed. The usual chips we find in mainstream portable digital audio player and smart phones and tablets generally has at last 4 DACs and 2 ADCs. Even though they are not all used by the specific products, this is also true of the SOC that is the heart of the economically-priced Sansa Clip+ and Fuze.

No, those are 1 stereo DAC devices. Two is actually rare in low power devices, and off hand I can't think of any dedicated MP3 players that do that. I think that Cirrus part above is aimed more at tablets and higher power devices, so probably they can afford a little more logic.

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Trouble is that in the real world, being disturbed by noise from the DACs is exceedingly rare...

I understand the need for high quality low volume product offerings with far greater capabilities than the minimum that is required for the mainstream market. If nothing else they facilitate the creation of media with the required quality levels since a product can't be better than the means used to create it. These products need not be justified based on the needs of the mainstream market but can make sense even when they vastly exceed the minimum need.

Yes, and yes.

But let me bring this thread back to the question of detecting D/A converter differences in an ABX test. I believe the SNR performance of many common audio products, combined with the ubiquitous use of generous amounts of digital volume control is sufficient to expose detectable differences in an ABX test. This does not mean that the general public is dissatisfied with these devices, and it does not imply that the converter noise is objectionable, but it does indicate that converter differences should be detectable in an ABX test. In fact, this has been my experience.

In the past, I posted the results of 2 ABX tests I conducted here at Benchmark:

In the two above tests, truncation in the MacBook's digital volume control was a dead give-away and resulted in a perfect score in the ABX tests.

The calculations I have presented in this current thread suggest that converter noise floor differences can also be sufficient to give away the identity of "X" in an ABX test (when using typical amounts of digital attenuation). SNR reduction and truncation are two distinct issues that can be caused by digital volume controls.

When digital volume control is used, it takes more than 16 equivalent bits to reproduce a 16-bit noise floor (1 extra equivalent bit is required for every 6.02 dB of digital attenuation). Again this does not mean that the casual user will be dissatisfied with the audio performance. However, the casual user MAY be able to detect the difference between two D/A converters.

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The following quote from NwAvGuy's Sansa Clip+ review sums up the situation:

"AUDIBLE HISS (added 2/23/11): Playing back a very low level signal with my most efficient headphones (the UE SuperFi's) the Clip+ has some very slightly audible hiss. Interestingly it seems (subjectively) slightly worse with the Rockbox firmware but I need to investigate that more. With more typical headphones there's zero audible hiss and even with the SuperFi's the hiss in the recording itself and/or background noise leaking past the headphones usually masks the slight hiss. So, in my opinion, it's not a problem unless you have uber-efficient headphones, listen to pristine recordings, and hate even a tiny bit of hiss."

In the two above tests, truncation in the MacBook's digital volume control was a dead give-away and resulted in a perfect score in the ABX tests.

I'm curious how you know that its digital volume control? Digital control introduces quantization noise, which is white. Analog volume control introduces thermal noise, which is also white. Short of plotting the noise power as a function of gain and checking the slope, how would you be sure you heard one or the other?

FWIW, most PCs use analog volume control (as the Intel onboard specifications use it). Obviously Apple can do whatever they want, but I'd be surprised if they did otherwise.

DAC linearity is important because most portable devices have digital volume controls that reduce the signal before the DAC

ha, hes wrong. I somehow missed that reading the review.

No. You have failed to understand your own post. You wrote:You couldn't buy an mp3 player that had digital volume control if you wanted to. They aren't made.

That the chip used in the Clip (assuming this is your evidence for your contention - you didn't bother saying why anybody should listen to you) has analog AND digital volume control still makes NWAVguy right and you wrong. Read what you wrote!

And if that chip isn't your evidence, then what is? Are people supposed to say "Yes; this man is angry and can't use apostrophes - clearly he must be in the right!"? No.

And I'm new here and have never taken a DAP apart, but requiring that someone you disagree with undertake the entire burden of proof while you should be assumed correct by default seems a bit much.

How exactly do I prove that something doesn't exist? I can point out that I've worked on drivers for lots of these devices and not one of them uses digital gain control, but I can't really prove it since I haven't worked on every single device in existence, just a lot of them.

Yes: your claim was inherently unprovable - which makes it silly - but if you could name a couple of major players then that would at least be indicative.

And you can claim to have written drivers, but so what? The Internet is full of people who claim to be special forces, CIA agents, and aliens - especially when they think it will help them win some silly debate. NWAVGuy is a reasonable expert witness because everyone here knows that he is competent enough to design the ODAC; all we know about you is that you can type.

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The question is not whether he is "the ultimate arbiter" but whether an ee engineer who has designed a DAC and who has take several DAP's apart is a reasonable source? Especially compared to none at all.

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I'm curious how you know that its digital volume control? Digital control introduces quantization noise, which is white. Analog volume control introduces thermal noise, which is also white. Short of plotting the noise power as a function of gain and checking the slope, how would you be sure you heard one or the other?

FWIW, most PCs use analog volume control (as the Intel onboard specifications use it). Obviously Apple can do whatever they want, but I'd be surprised if they did otherwise.

Digital volume control introduces noise with a white spectrum if TPDF dither is properly applied. The spectrum is not white when truncation occurs. Amplitude linearity is also lost when dither is not applied. We verified that truncation was occurring.

Most newer media players and newer operating systems have 24-bit volume controls. These may or may not be dithered (depending on the OS or player selected). One problem is that some hardware imposes a 16-bit bottleneck between the DSP and the DAC. The interface between 24-bit DSP (or higher) and 16-bit hardware is still poorly addressed. Computer systems with newer 24-bit hardware are less-likely to have truncation problems (provided all of the software is up-to-date).

That the chip used in the Clip (assuming this is your evidence for your contention - you didn't bother saying why anybody should listen to you) has analog AND digital volume control still makes NWAVguy right and you wrong. Read what you wrote!

And if that chip isn't your evidence, then what is? Are people supposed to say "Yes; this man is angry and can't use apostrophes - clearly he must be in the right!"? No.

Well I wrote the volume control code used in that review, and its open source, so you can read it if you want:

And you can claim to have written drivers, but so what? The Internet is full of people who claim to be special forces, CIA agents, and aliens - especially when they think it will help them win some silly debate. NWAVGuy is a reasonable expert witness because everyone here knows that he is competent enough to design the ODAC; all we know about you is that you can type.

You can easily google my username and verify that I've written this stuff. Or just search on these forums. I post about this stuff a lot, and plenty of people here know me, NWAVguy included.

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What I find interesting is the fact that 100% of all of the contemporary AVRs that I have examined have both DSPs and digitally controlled analog volume controls.

There is a good reason for this (as I am sure you are aware):

The digitally controlled analog volume control allows control of analog sources without inserting an A/D converter and D/A converter (codec). The analog volume control chips have certain performance limitations (and costs) but some engineers have chosen this option. In many cases the A/D and D/A components are available in the box, but input signal level variations can make it difficult to use a digital gain solution. Low-level input signals place a significant burden on the performance of the A/D as the converter noise may get amplified by digital gain.

We take a similar approach with the DAC2 converter, except that the analog gain control is accomplished with a digitally-controlled motor-driven pot. We did this to avoid inserting a codec when selecting analog inputs.

Yes: your claim was inherently unprovable - which makes it silly - but if you could name a couple of major players then that would at least be indicative.

Based on the other contention, namely that almost all players implement volume digitally, you would think his claim would be easily falsified. There's quite a disparity from that and inherently unprovable, no? I mean, you already think you disproved it if I am to take your contention seriously that NwAvGuy is right and Saratoga is wrong. Of course at the time of this edit, I think it has been conceded by John that both Apple and Sansa use an analog volume control. Are these major enough players for you?

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I'm curious how you know that its digital volume control? Digital control introduces quantization noise, which is white. Analog volume control introduces thermal noise, which is also white. Short of plotting the noise power as a function of gain and checking the slope, how would you be sure you heard one or the other?

FWIW, most PCs use analog volume control (as the Intel onboard specifications use it). Obviously Apple can do whatever they want, but I'd be surprised if they did otherwise.

Digital volume control introduces noise with a white spectrum if TPDF dither is properly applied. The spectrum is not white when truncation occurs. Amplitude linearity is also lost when dither is not applied. We verified that truncation was occurring.

I don't follow you. How does truncation imply digital volume control? And how do you know you were hearing it? You were apparently convinced it was happening on iPods, and that is not the case. How certain are you that you're not mistaken here?

One problem is that some hardware imposes a 16-bit bottleneck between the DSP and the DAC. The interface between 24-bit DSP (or higher) and 16-bit hardware is still poorly addressed. Computer systems with newer 24-bit hardware are less-likely to have truncation problems (provided all of the software is up-to-date).

What hardware is this? PCI, I2S, etc all handle 24 bit fine and have for many years. Do you mean USB DACs? Be specific.

One block diagram (page 7 of the data sheet) shows a volume control feature in the headphone amplifier (following the D/A converter). This implies that the unit has some analog volume control capability.

However, a more detailed block diagram on page 8 shows digital mixing and audio processing before the D/A converter (in the digital domain).

The truth is that the MAS3539F uses both analog and digital volume control. The following is a quote from page 10 of the data sheet:

"To minimize quantization noise, the main volume controlis automatically split into a digital and an analogpart. The volume range is ?114...+12 dB with an additionalmute position. A balance function is provided."

Register 00 11 controls the main volume. This is "splitbetween a digital and an analog function" (see page 51 of the data sheet).

Bottom line, some MP3 players may use a combination of analog and digital gain control (see MAS3539F) . Others only use digital gain control (see CS42L73).